I've only ran 1 so far (second one is tomorrow night if all goes well) so I do not have any expert advice, but wanted to share what I did. For my first, I tried to start in the back. That way the pros could get started and be on their way, leaving me more room to adjust to everything going on. Once I started, I tried to find my regular pace and then just stick with it. It was kind of hard though because my adrenaline was going so fast that I couldn't tell what my pace was. I just tried to relax and have fun. Good luck tomorrow.
Jean